Simulation of flows through submerged vegetation patches using macroscopic turbulence models

Abstract

Macroscopic approach incorporating the spatial averaging procedure is commonly used to investigate turbulent flows in porous media, terrestrial and aquatic canopies. In this work the hydrodynamics of flows through a semi-rigid vegetation patch (VP) was investigated with two macroscopic turbulence models. We modified the Reynolods Averaged Navier Stokes (RANS) equations to obtain the Volume Averaged (VARANS) equations and performed simulations using the open source code OpenFOAM. The numerical results of gradually varied flows over submerged VPs are compared with the corresponding experimental measurements. The results show that the macroscopic turbulence models simulate the velocity profiles with acceptable accuracy. The increase of vegetation density generates higher Reynolds stress around the top of vegetation and smaller velocity inside the VP. The two models perform differently in the computation of Reynolds stress, with the profiles from the model of Uittenbogaard (2003) requiring a shorter distance to reach the uniform state for the case of low vegetation density. Further works will be carried out to identify the cause of difference and to achieve a refined macroscopic turbulence model.